1. Technical Field
Embodiments of the invention relate to semiconductor devices executing a test operation by repeatedly writing and reading data and semiconductor systems including the same.
2. Related Art
Semiconductor devices may be designed and fabricated to include a test mode function for evaluating the operation thereof. That is, various parameters of the semiconductor devices may be measured in a test mode at a wafer level or at a package level and the tested semiconductor devices may be sorted into good chips or failed chips according to the test results.
More specifically, each of the semiconductor devices may execute a read operation or a write operation to output or receive a plurality of data. The read operation may be executed to output data stored in memory cells through pads connected to input/output (I/O) lines. The write operation may be executed to store data received through the pads into the memory cells. That is, the data may be transmitted through the pads of the semiconductor device so that the semiconductor device communicates with an external device.
In order to test or evaluate the semiconductor device, the semiconductor device may execute the read operation or the write operation to output the data stored therein or to receive external data and may sense logic levels of the data to discriminate whether internal circuits of the semiconductor device normally operate or not.
Meanwhile, if the number of data bits whose phases are changed when the data are transmitted in the semiconductor device increases, a simultaneous switching noise (SSN) phenomenon and an inter-symbol interface (ISI) phenomenon may occur more frequently. Thus, a data bus inversion (DBI) scheme has been used to suppress the SSN phenomenon and the ISI phenomenon. If data outputted from an external device are transmitted to the semiconductor device using the DBI scheme, the data have to be transmitted together with a DBI signal including information on whether the data are inverted.